

Ven. 08/11/2024 09:00 Andromede, Bâtiment 11, Etage 3 Séminaire
MARTINELLI Alessandro (L2C)
A microscopic look at glassy dynamics: residual stresses and plasticity in hard and soft glasses
Sommaire:
Residual stresses and plasticity are wellknown companions of all glassy materials. In the years, it was understood that macroscopic stress fields can be tuned to severely affect some physical properties of the material, like for example the strength in tempered glasses. Despite this, their nature at the microscopic length scale is still unclear: their behaviour is tightly linked to plasticity, i.e. local nonaffine deformations that in glasses behave as stress sources coupled to the elasticity of the material.
In this talk I will discuss recent XRay Photon Correlation Spectroscopy (XPCS) results exploring the interplay between plasticity, stress fields and the microscopic dynamics in very different systems i.e., colloidal and atomic glasses.
In the colloidal system, I will show how the dynamics is dominated by residual stresses trappedin during the preparation procedure, which give rise to a very rich phenomenology in the observed dynamical properties, as the presence of compressed relaxation functions, ballistic dynamics and dynamical heterogeneities [1]. In the second part of the talk, I will focus on oxide glasses illuminated with hard Xrays. I will show that the absorbed photons create point defects which behave as plastic regions, and their number is directly controlled by the delivered dose [2]. Following the atomic dynamics on different lengthscales, I will show how the glass can behave both elastically and plastically, eventually reaching a state where the microscopic dynamical properties resemble that of a flowing system [2].
Finally, I will present a CNRS project aiming at pushing our understanding of plasticity at the microscopic lengthscale. I will propose to leverage the properties of new thermosensitive colloidal glasses to investigate plastic activity for different level of glass equilibration (i.e., residual stresses) and external applied perturbations, combining cuttingedge experiments involving rheology, time and space resolved visible scattering and synchrotronbased Xray photon correlation.
[1] F. Dallari, A. Martinelli, et al., Sci. Adv. 6(12), eaaz2982 (2020).
[2] A. Martinelli et al., Phys. Rev. X CR, 04LF31 (2023). Pour plus d'informations, merci de contacter Merindol R.
